This invention relates broadly to electromechanical control devices and, more particularly, pertains to a compact, high current, low resistance, bistable relay particularly useful in handling the electrical requirements of a growing number of automotive accessories expected to be operated at voltages exceeding the current standard 24 volts dc.
As explained in U.S. Pat. No. 6,084,488 issued to Macbeth et al., Jul. 4, 2000, electromechanical relays of the type with which this invention is concerned include one or more pairs of movable contacts that can be selectively brought into engagement to complete an electrical circuit called xe2x80x9ccontact makexe2x80x9d, or moved apart, called xe2x80x9ccontact breakxe2x80x9d, to open the circuit. During either make or break when the contacts are at some very small separation ( less than 1xc3x9710xe2x88x926 m), an arc is formed. A variety of techniques have been employed in the past to minimize the amount of arcing, and/or compensate for the arcing, to provide a relay that continues to operate effectively.
When an arc occurs, it is common for material to be transferred from one relay contact to another, and in many cases, an actual weld, albeit a small one, is formed between the contacts. In normally open contacts, for example, if a weld is formed between contacts when the contacts are closed, the weld may tend to hold the contacts closed when operating forces are removed, and this may prevent the relay from opening as desired. Typically, electromechanical relays include a solenoid for physically bringing the contacts together, and rely on a spring to force the contacts open when the solenoid is deenergized.
It is common to arrange relay contacts so that they engage and/or separate with a combination of relative movements, including opening and closing movements generally perpendicular to the surfaces of the contacts, and wiping movements generally transverse to the surface. The relative wiping movement of the contacts reduces the tendency for arcing to create strong welds during closure and adds a torsional force to help break welds on demand to open, therefore making the relay more reliable. In addition, and equally important for reliability and high performance in systems requiring a very low resistance device, a properly designed contact wipe will remove the thin but high resistance tarnish film which occurs on Nobel metals.
In the aforementioned ""488 patent, a compact high current relay is provided having first and second fixed contacts connected in circuit relationship with the apparatus to be controlled. An elongated bus bar has first and second movable contacts at opposite ends thereof, the bus bar characterized by a stiffness such that upon application of a first predetermined force to the bus bar between the contacts, the bus bar flexes and the movable contacts both tilt and wipe with respect to the first and second fixed contacts. A solenoid is connected to the bus bar between the first and second contacts for exerting a force on the bus bar greater than the predetermined force.
While the Macbeth et al. patent is generally satisfactory for relays with a flexible bus bar design, it remains desirable to provide a differently styled relay having unique structure to suppress arcing, to allow wiping of the contacts as the contacts are closed, and to apply a strong torsional force to the contacts on opening. Minimization of both the total resistance across the device and the power required to hold the device in either the contact open or the contact closed state are also desired.
It is a general object of the present invention to provide an arc suppressing high current relay with enhanced DC interruption capability at voltages exceeding those of typical relays.
It is also an object of the present invention to provide an insulator receiving structure for the fixed contacts of the relay that will enable cooling of the arc.
It is an additional object of the present invention to provide a means to move the arc towards the insulator in order to enhance cooling.
It is an additional object of the present invention to provide an improved movable contact assembly which will effectively wipe the fixed contacts of the relay in a manner that prevents tarnish build up between the contacts and also minimize the chance of hard welds.
It is an additional object of the present invention to provide an improved movable contact assembly that will provide a torsional component of force and increase the weld break capability of the device on contact break.
It is an additional object of the current invention to provide a device which can remain fixed in either the open or closed position after being commanded there by the coil and the power to the coil is subsequently removed.
In one aspect of the invention, there is provided a relay subject to arcing when contacts make or break, and susceptible to welding and erosion due to arcing. The relay includes a solenoid having a plunger movable into and out of the solenoid. The solenoid is comprised of two sets of windings such that power may be applied to the solenoid to create a field with the north pole towards the contacts in the one instance and with the south pole directed towards the contacts in the other. A permanent magnet with a field which could be oriented either such that its north pole faces towards the contacts or that its south pole faces the contacts, is included in the magnetic circuit with the plunger part of its magnetic path. Upon application of power to the solenoid that provides a supplemental field to the magnet, the plunger will move into the solenoid and latch. Upon subsequently removing the power to the solenoid the device will remain in the latched position. Upon application of power to the solenoid creating a field opposing the permanent magnet, the plunger will unlatch and move forward out of the solenoid. Upon subsequent removal of power to the solenoid the solenoid will remain in its forward position. A pair of fixed contacts is provided along with a movable bridge assembly having a pair of movable contacts adapted to engage and disengage the fixed contacts upon unlatch and latch of the plunger. The bridge assembly is connected via a ball joint arrangement to the solenoid plunger, the ball joint arrangement enabling the movable contact to move laterally with respect to the stationary contact causing contact wipe to occur and thin film tarnish to be removed from the contacts on closing. Additionally, the ball joint arrangement provides a torsional force to break welds on opening. An insulator surrounds the movable contacts for cooling the arc between the movable and fixed contacts. The solenoid is supported in a generally rectangular frame having an end plate. The fixed contacts are carried on outwardly and downwardly angled legs of a pair of generally L-shaped brackets. The relay has a housing for supporting the solenoid in its frame, the insulator, the movable bridge assembly and the L-shaped brackets. The contacts and contact bus are oriented relative to the field of the permanent magnet and opening solenoid such that a current through the opening contacts will experience a force due to that field. The contacts and contact bus are also oriented such that a current through them will also experience a force due to their xe2x80x9cself field.xe2x80x9d The force experienced by the current due to the permanent magnet and the solenoid will supplement the force due to the self field for current flowing in one direction and partially supplement it and partially oppose it for current flowing in the opposite direction. The force of the self-field on the current is towards the insulator regardless of the direction of the current flow. The plunger has a cylindrical portion and a spherical portion. The spherical portion is received within a swivel cap attached to the movable bridge assembly to define a swivel arrangement for the movable contacts on the bridge assembly. The insulator is preferably constructed of LEXAN polycarbonate. The relay housing has one cavity for holding the solenoid in its frame, and another cavity for holding the insulator, the movable bridge assembly and the angled legs of the L-shaped brackets. The insulator is formed with pockets for receiving lowermost ends of the angled legs of the L-shaped brackets. The L-shaped brackets include horizontal legs integrally connected to the outwardly and downwardly angled legs. The outwardly and downwardly angled legs are disposed at an angle of about 95 degrees relative to the horizontal legs. A coil spring has one end disposed against the end plate and a second end disposed against a rearward end of the bridge assembly.
In another aspect of the invention, a relay has a pair of fixed contacts, a pair of movable contacts adapted to be engaged and disengaged with the fixed contacts, and a solenoid having a plunger movable into and out of the solenoid, the plunger having an outer end operably connected to the movable contacts. The invention is improved by a motion translating and preferably a ball joint arrangement interconnecting the plunger and the movable contacts to enable wiping of the contacts on make to remove thin film tarnish and to provide torsional force to aid in the breaking of welds on opening. The invention is further improved by an insulator surrounding the movable contacts for cooling the arcing. The ball joint arrangement provides for swivel movement of the movable contacts. The ball joint arrangement includes a spherical portion formed on one end of the plunger, a cylindrical swivel cap liner for receiving the spherical portion of the plunger, and a cylindrical swivel cap for receiving the liner, the swivel cap being attached to the movable contacts. The insulator includes a top wall overlying the movable contacts. The fixed contacts are carried on outwardly and downwardly angled legs that are received in a pair of pockets formed in the insulator. The insulator is constructed of a gas expelling material. The contacts and contact bus are oriented relative to the field of the permanent magnet and opening solenoid such that a current through the opening contacts will experience a force due to that field. The contacts and contact bus are also oriented such that a current through them will also experience a force due to their xe2x80x9cself field.xe2x80x9d The force experienced by the current due to the permanent magnet and the solenoid will supplement the force due to the self field for current flowing in one direction and partially supplement it and partially oppose it for current flowing in the opposite direction. The force of the self-field on the current is towards the insulator regardless of the direction of the current flow.
In yet another aspect of the invention, a relay includes a solenoid having a plunger movable into and out of the solenoid. The solenoid is comprised of two sets of windings such that power may be applied to the solenoid to create a field with the north pole towards the contacts in the one instance and with the south pole directed towards the contacts in the other. A permanent magnet with a field which could be oriented either such that its north pole faces towards the contacts or that its south pole faces the contacts, is included in the magnetic circuit with the plunger part of its magnetic path. Upon application of power to the solenoid that provides a supplemental field to the magnet, the plunger will move into the solenoid and latch. Upon subsequently removing the power to the solenoid the device will remain in the latched position. Upon application of power to the solenoid creating a field opposing the permanent magnet, the plunger will unlatch and move forward out of the solenoid. Upon subsequent removal of power to the solenoid the solenoid will remain in its forward position. A frame is provided for holding the solenoid. A pair of generally L-shaped brackets has horizontal legs integrally formed with outwardly and downwardly angled legs carrying a pair of fixed contacts. A movable bridge assembly is provided with a pair of movable contacts adapted to engage and disengage the fixed contacts upon respective unlatch and latch of the plunger. The bridge assembly is connected via a ball joint arrangement to the solenoid plunger. The ball joint arrangement enables wiping of the contacts and removal of thin film tarnish on make and also provides a torsional force to aid in breaking of welds on opening. A coil spring surrounds the ball joint arrangement and has one end disposed against the frame and another end disposed against the bridge assembly. An insulator surrounds the movable contacts for cooling the arc. The contacts and contact bus are oriented relative to the field of the permanent magnet and opening solenoid such that a current through the opening contacts will experience a force due to that field. The contacts and contact bus are also oriented such that a current through them will also experience a force due to their xe2x80x9cself field.xe2x80x9d The force experienced by the current due to the permanent magnet and the solenoid will supplement the force due to the self field for current flowing in one direction and partially supplement it and partially oppose it for current flowing in the opposite direction. The force of the self field on the current is towards the insulator regardless of the direction of the current flow.